Back pain is among the top contributors to disability among Americans and is associated with considerable cost to the US economy. Despite established practice guidelines that recommend conservative approaches, clinical management of nonspecific back pain (i.e., back pain that is not caused by pathologic etiology) varies, with evidence of overuse of opioid analgesics, early diagnostic imaging, and specialty care. Older adults in particular receive poorer care for nonspecific back pain than their younger counterparts. While nonspecific back pain is one of the top reasons adults visit physicians, it also happens to be one of the most common conditions treated by complementary and alternative medicine (CAM) providers who rely on conservative management. In the US, the chiropractic profession is the largest and most organized CAM group, and chiropractic care is the only CAM service covered by Medicare. However, current information available to health policymakers lacks a fundamental understanding of the potential indirect effects of chiropractic care in Medicare. The overall objective of this project is to rigorously examine the relationship between availability of chiropractic care and utilization, expenditures, and care for nonspecific back pain. Our central hypothesis is that chiropractic care is being used as a substitute for ambulatory medical services and affects both expenditures and nonspecific back pain care. This research project has the following two aims: (1) Among older adults, determine the extent to which availability of chiropractic care influences use of and expenditures on ambulatory medical services (e.g., primary care, specialty care, and emergency room visits) for nonspecific back pain and (2) Among older adults, determine the extent to which availability of chiropractic care influences clinical management of nonspecific back pain. Our approach is innovative because it departs from the current status quo by performing a real-world, natural experiment using Medicare patients who relocated. As each patient serves as his or her own control, this rigorous study design is better suited to identify causal relationships and will allow us the unique opportunity to observe the effect of a change in chiropractic care availability. In order to measure availability of chiropractic care and other health services, we will apply novel geographic information system (GIS) tools. This proposed project is significant because it will provide timely information for health policymakers to anticipate effects of healthcare system redesign; specifically, how inclusion of a CAM service in a national health insurance system impacts care of older adults with nonspecific back pain.